It is generally believed that a Multi-Service Access Node (MSAN) is composed of narrowband service shelves and broadband service shelves.
Currently, in the pure narrowband application field, the access device is designed with a slave shelf. This solution is based on a Time Division Multiplex (TDM) system, where the master shelf and the slave shelf are physically connected through E1, and logically interconnected through an internal private protocol.
In the application field of the broadband digital subscriber line, a single-shelf solution is applied in an access device such as a Digital Subscriber Line Access Multiplexer (DSLAM), and no slave shelf is supported. With the increase of users, more and more devices are added to the communication system, and more nodes need to be managed, thus making the management complicated.
In the Asynchronous Transfer Mode (ATM) application field, the Broadband Loop Emulation Service (BLES) does not involve the networking application of slave shelves either.
In the application field that integrates broadband and narrowband (for example, the BLES protocol is extended to the Extended Broadband Loop Emulation Service (XBLES) protocol), the extended protocol defines communication between the Plain Old Telephone Service (POTS) subscriber board and the protocol processing board, and voice services are implemented on the basis of the Ethernet, without involving the networking application of the broadband/narrowband slave shelves.
In a technical solution in the related art, a narrowband access device, for example, a pure narrowband device, or an access media gateway, may provide master-and-slave shelf networking through a TDM network, where the master shelf and the slave shelf are physically connected through E1 and logically interconnected through an internal private protocol. If the master shelf and the slave shelf are in different equipment rooms, a transmission system is required between them. The transmission system may be regarded as transparent. If the master shelf and the slave shelf are in the same rack, the master shelf and the slave shelf may be interconnected through a HighWay (HW) in view of a short distance between them. In E1/HW interconnection mode, the communication between the master shelf and the slave shelf is defined by the manufacturer, without passing through the devices from other manufacturers. Even if a transmission system is deployed between the master shelf and the slave shelf, the privacy of the network is still ensured.
With respect to management, communication may be implemented between the master shelf and the Network Management System (NMS) in Ethernet in-band mode, or Ethernet out-band mode, or E1 in-band mode. The Ethernet may be a Fast Ethernet (FE) or a Gigabit Ethernet (GE). However, the foregoing master-and-slave shelf networking solution can only be based on a TDM system, and cannot be transplanted to an Ethernet system simply. If the communication between the master shelf and the slave shelf passes through a layer-2 or layer-3 switch or router from manufacturers, the circumstance becomes much more complicated.
In another technical solution in the related art, a DSLAM works as an access device by using a single-shelf solution. For the NMS, each broadband shelf is a stand-alone device, namely, a stand-alone network element. Each broadband device may be connected to the NMS in FE in-band or out-band mode or GE in-band or out-band mode.
In this solution, however, each shelf is a stand-alone network element, without supporting slave shelf networking. Even for multiple broadband shelves in the same rack, each broadband shelf needs to be managed as a stand-alone network element. Therefore, many nodes need to be managed; many Internet Protocol (IP) addresses need to be occupied; and the management is complicated. Moreover, all the broadband shelves need to provide the same main control board, which is costly.
In another technical solution in the related art, for an MSAN, a service shelf may hold a narrowband voice service board and a broadband service board at the same time. Therefore, a service shelf may be logically divided into a narrowband service shelf and a broadband service shelf. Generally, for ease of management, an operator configures broadband service boards in one shelf, and configures narrowband service boards in the other shelf.
If a TDM bus is applied between the narrowband service shelves, the master-slave shelf solution is supported, and all the shelves are embodied as one network element to the outside; if an Ethernet bus is applied between the narrowband service shelves, no slave shelf is supported, and each narrowband service shelf is embodied as a stand-alone network element to the outside. With respect to broadband service shelves, each broadband service shelf is embodied as a stand-alone network element to the outside.
In an MSAN where the narrowband system is based on a TDM bus but the broadband device is based on an Ethernet bus, all narrowband service shelves may constitute one network element, and each broadband service shelf is a stand-alone network element. If there is only one broadband service shelf, the broadband service shelf may be combined with the narrowband service shelves into the same network element. The management is rather complicated especially in an MSAN where one rack contains multiple narrowband service shelves or broadband service shelves.
For an MSAN based on the Ethernet completely, no slave shelf is supported, and each service shelf is embodied as a stand-alone network element to the outside. In this case, the management is complicated, and each shelf requires an IP address.
Therefore, the Ethernet-based slave shelf cascade in the related art involves complicated network management and high costs of maintenance and management.